What is sarcoidosis?
Sarcoidosis is an inflammatory disease that affects one or more organs but most commonly affects the lungs and lymph glands. As a result of the inflammation, abnormal lumps or nodules (called granulomas) form in one or more organs of the body. These granulomas may change the normal structure and possibly the function of the affected organ(s).
How does the condition progress?
Although no one can predict how sarcoidosis will progress in an individual patient, some clues as to disease course can be gained from patient symptoms, findings from physical and laboratory studies, and patient race. For example, a sudden onset of general symptoms--such as weight loss, fatigue, fever, or just an overall feeling of ill health--usually means that the course of sarcoidosis will be relatively short and mild in severity. Symptoms of shortness of breath and some types of skin involvement mean that sarcoidosis will be more long-lasting and severe.
In Caucasians, the disease often appears suddenly, which usually indicates a more mild form of the disease that is of short duration. African-Americans and Puerto Ricans, on the other hand, tend to develop the more long-term and severe form of the disease.
In the United States, the lungs are often the most common site of initial symptoms for those who experience a gradual onset of their long-term disease. Lung symptoms are common in African-Americans, Puerto Ricans, and Scandinavians. Persistent dry cough, fatigue, and shortness of breath are the most common initial lung-related complaints.
Some patients who experience sudden onset of disease have Lofgren’s syndrome, a form of sarcoidosis that affects the lymph nodes and is accompanied by a skin condition that produces red nodules under the skin, as well as fever and arthritis pain. Patients with Lofgren’s syndrome usually can expect a good outcome; the disease goes away on its own in 85% to 90% of people.
How sarcoidosis progresses: What happens at the tissue level
At the tissue or cellular level, sarcoidosis disease progression can be divided into three phases:
- The first change that is seen is inflammation.
- In the second phase, granulomas form. Granulomas are masses or nodules of chronically inflamed tissue and are the classic sign of sarcoidosis Granulomas are the body’s attempt to wall off or isolate organisms and other foreign particles that are difficult for the immune system to eradicate or dispose of.
- In the third phase, fibrosis (scarring) of tissues or organs occurs. If scarring is extensive in a vital organ, sarcoidosis is sometimes fatal.
In some people, the disease advances from one phase to the next in the tissues of the organ affected. In others, the different phases of tissue changes take place within the same organ at the same time. In many patients with sarcoidosis, the granulomas go away on their own in 2 to 3 years without the patient knowing or doing anything about them. In others, the granulomas progress to irreversible fibrosis. The immune system changes that allow one person’s disease to progress while another person’s disease resolves are not well understood and continue to be investigated.
Does sarcoidosis run in families?
While the latest research does appear to indicate a genetic susceptibility to the disease, more research is needed to clearly identify and confirm the genes involved. However, numerous reports have revealed racial/ethnic and family-line occurrences, including the following:
- Irish immigrants in London have a three-fold likelihood of developing sarcoidosis compared with native Londoners.
- Natives of Martinique living in France have an eight-fold higher chance of developing the disease compared with the native French population.
- African-Americans face a 4 to 17 times greater risk of the disease compared with Caucasians.
- Within individual families, the presence of the disease in a first- or second-degree relative increases the risk by nearly five-fold.
Still other types of disease clusters have been identified, including seasonal and occupational clustering. Researchers in Greece, Spain, and Japan have reported a clustering of diagnoses of sarcoidosis in the months of March to May, April to June, and June to July. In the United States, a higher percentage of cases of sarcoidosis have been reported in health care workers, naval aircraft servicemen, and firefighters.
What causes sarcoidosis?
The exact cause of sarcoidosis is not known. The disease can appear suddenly and then disappear, or it can develop gradually and produce symptoms that come and go for a lifetime.
Researchers believe that the disease is caused by an abnormal immune response. (The body’s defense system does not react as it should to a foreign substance "intruder.") In a healthy person, inflammation occurs as the cells of the body’s immune system come together to fight the intruder at an organ or tissue site. In a person with sarcoidosis, however, cells that come to fight end up clumping together into small lumps called granulomas.
It’s still uncertain which foreign substance "triggers" the body’s abnormal response. Some researchers suggest that fungi, viruses, or bacteria are likely triggers. In fact, cases of sarcoidosis have occurred in groups of people who had close contact with each other, as well as in recipients of heart, lung and bone marrow transplants. But, so far, no data have been able to convincingly and consistently establish this "infectious" connection as the cause of the disease. However, some types of bacteria have recently emerged as possible candidates and continue to be closely studied.
What are the symptoms of sarcoidosis?
The symptoms of sarcoidosis can vary greatly from individual to individual, and depend on which tissues and organs are affected. In some people, symptoms may begin suddenly and/or severely and subside in a short period of time.
Others may have no outward symptoms at all, even though organs are affected. Still others may have symptoms that appear slowly and subtly, but last or recur over a long time span.
Most common initial symptoms:
- Shortness of breath (dyspnea)
- Cough that won’t go away
- Reddish bumps or patches on the skin or under the skin
- Enlarged lymph glands in the chest and around the lungs that produces cough and shortness of breath
- Fever, weight loss, fatigue, night sweats, general feeling of ill health
Other disease characteristics include:
- Red and teary eyes or blurred vision
- Swollen and painful joints
- Enlarged lymph glands in the neck, armpits, and groin
- Nasal stuffiness and hoarse voice
- Pain in the hands, feet, or other bony areas due to the formation of cysts (an abnormal sac-like growth) in bones
- Kidney stone formation
- Development of abnormal or missed beats (arrhythmias), inflammation of the covering of the heart (pericarditis), or heart failure
- Nervous system effects include hearing loss, meningitis, seizures or psychiatric disorders (for example, dementia, depression, psychosis)